1. Field of the Invention
The invention is an in-mold label film with low thermal conductivity. The invention is further the use of these in-mold label films in both large area label applications, and to decrease the mold residence time for in-mold processes. The invention still further is the processes for the manufacture of these in-mold films and labels.
2. Technology Review
It has been know for a number of years to manufacture and distribute polymer films for the use as facestock in labels. When a plastic container such as a polyethylene squeeze bottle is used to package a product such as a hair shampoo, a package using a polymeric label is generally more appealing to consumers than a package using a paper label. In many applications the use of polymeric labels is required for reasons of appearance, handling, performance, moisture-resistance, conformability, durability and compatibility with the container to be labeled.
In-mold labelling has significant advantages over methods commonly used in the past to label plastic containers with polymeric labels. The most common of these previous methods involve the use of liner-carried pressure sensitive adhesive labels, or liner carried heat activatable adhesive labels. To produce the liner carried labels, a laminating step is performed to sandwich a layer of adhesive between a web of label stock and a web of silicone-coated paper which is to function as a carrier or release liner, the label stock is printed, the ink is dried by heating elements or ultraviolet radiation, separate labels are cut from the label stock by passing the combination through a rotary-die or flat-bed cutting station, and the matrix of waste or trim label stock surrounding the labels is stripped and discarded or recycled. What remains is a succession of individual labels releasably carried on the release liner. Use of these types of methods results in high costs due to the use of a release liner, and the ecological difficulties in disposing of the liner and the trim.
In contrast, in-mold labeling avoids the use of any release liner or carrier. During in-mold labelling with polymeric labels, self-supported or free-film polymeric label stock is combined with heat-activatable adhesive, printed, die-cut and then arranged for deployment, as by being magazine-loaded as a series or stack of linerless labels, or by other means. The polymeric labels are then sequentially deployed on the molding surface of a blow mold to be bonded onto successive hot plastic substrates or containers. The blow molded parisons are expanded against the molding surface and the in-mold label which activates and bonds the heat-activatable adhesive to the blown plastic substrate or container.
Despite the advantages of in-mold labeling over liner-carried labelling, the commercially successful accomplishment of in-mold labelling with polymeric labels has been inhibited by a problem that was not encountered with either liner-carried labelling with polymeric labels or in-mold labelling using paper labels. This problem was the unacceptable quality of the bond between the plastic substrate or container and the label film, and the further difficulties experienced in large area label applications involving unacceptable blistering and peeling of these label films.